As discussed at the International Symposium for Protecting Global Warming Phenomena held in Kyoto on December 1997, the problem of rising sea level is expected in the next century. Known techniques for protecting a coastal land from a rise in the sea level had been to increase the bulk and height of a levee or barrier. The inventor of the present invention has found that the technique for building a tidal power generation system operated during high tide in a bay, which was disclosed in Japanese Patent Application No. H9-200818 by the same inventor as the present invention, can be applied to protect the coast line from a rise of the surface of the sea, and that the tidal water generation system can be constructed at any coastline on the earth.
In H9-200818, in order to convert the tidal range in a bay into energy, a tidal channel is built on one side of or in the center of the bay, so that the channel extends from the bay entrance to the depth of the bay. The tidal range is kept in the natural state. Then, a multiplicity of rectangular ponds, with the coastline as one side of each rectangle, are constructed on one side or both sides of the channel. Each pond is surrounded by a dam, which includes one or more pump-turbines therein. To generate electric power during a high tide, the water level of each pond must always be kept lower than the average sea level. To be more precise, during nighttime and low tide, the pumps are driven to lower the water level of each pond, using excess electric power supplied from the power network. Then, during daytime and high tide, the seawater is introduced in each pond by the turbines until the water level of the pond reaches the preset level. This system can achieve at least 100% efficiency of pumped storage power generation. In order to construct this system economically, a single pond is first constructed as a unit. Then, after the construction of the first pond is completed, the next pond is constructed adjacent to the first pond, while the first pond is used to generate electric power. In this manner, all ponds can be successively constructed in due course.